My view is this: Sonny wanted to play for the people, specifically the middle class. He did not want to play avant garde; he wanted to groove. In a way, he took a very challenging stance: to force his hardcore jazz audience to accept musicians like Stanley Clarke, George Duke and Larry Coryell as real, substantive jazz musicians. He reaffirmed that melody, rhythm and (perhaps most of all) approachability were core to his jazz experience. He wanted to be the opposite of an elitist.
Music for the plebs?
Hey, the guy just wanted to waltz.